This invention relates to a method of rendering a surface anticorrosive by depositing a thin layer of boron phosphide thereon. It is also directed to a method of rendering specifically, a semiconductive layer anticorrosive. This invention also relates to the use of a CVD (chemical vapor deposition) grown film of boron phosphide on a photoanode, e.g., an n-Si photoanode, of a photoelectrochemical cell as a stable photoelectrode layer and corrosion resistant protecting film for said photoanode.
It is known from the article "Crystal Growth of Boron Monophosphide Using a B.sub.2 H.sub.6 -Ph.sub.3 -H.sub.2 System" by Shohno, Ohtake, and Bloem in Journal of Crystal Growth, Vol. 45, pp 187-191 (1978), to epitaxially grow BP layers on Si wafers in the thermal reaction of a B.sub.2 H.sub.6 -PH.sub.3 mixture in hydrogen. More specifically, the BP layer is grown in a horizontal CVD system for use as a conductive layer grown on a silicon substrate. Moreover, the article discusses the growth of either n-type BP or p-type BP for determination of the electrical properties of the BP layer. However, there is no explanation of how the parameters of the process can be varied to modify the grown film to obtain specifically desired electrical properties.
U.S. Pat. No. 2,677,714 to Auwarter discloses an optical-electrical conversion device comprising a light-permeable metal electrode. The metal layer is composed of a member of the group consisting of gold, silver, copper and copper alloy, and has a cover layer composed of a member of the group consisting of silicon and metal oxides, metal sulfides, metal fluorides, and metal phosphides. However, there is no discussion in said patent of the use of boron phosphide as both an electrode material and as an anticorrosive layer on the n-type anode of a photoelectrochemical cell such as a solar converter.
U.S. Pat. No. 4,268,711 to Gurev is of interest merely for the disclosure of a method of forming a solar cell cover in an approved apparatus. However, the patent merely discloses the forming of a mixed oxide and/or nitride solid coating on the surface of an article for physically protecting the surface of a solar cell.
U.S. Pat. No. 2,677,715 to Auwarter discloses an optical-electrical conversion device comprising a light-permeable metal electrode, such as gold, silver, copper, etc. There is an incidental disclosure of the use of phosphides as a dielectric.
There is no suggestion in any of the references that BP is useful as a corrosion resistant coating, and especially for a photoelectrode, i.e., a photoanode of photoelectrochemical cells. These references also fail to appreciate that BP can be used to render other surfaces, prone to corrosion, anticorrosive. More specifically, these references fail to show or suggest the use of BP in semiconductor device surface application, and particularly those exposed to corrosive aqueous environments.